Device for the treatment of article flows and method therefor

ABSTRACT

A device  10  for generating an output flow of articles, starting from a flow of incoming articles having a given advancing velocity, includes a screw conveyor to receive longitudinally the flow of incoming articles. The conveyor in question comprises at least one screw the helix of which is susceptible to interact with the advancing of articles to determine their conveying by the screw itself. The rotational velocity of the screw is adjustable for varying the conveying velocity of the articles with respect to the initial advancing velocity. In particular, it is possible to act so that the conveying velocity of the articles by the screw is a sub-multiple of the initial advancing velocity so that the output flow of articles includes groups of stacked articles. Each group includes a number of articles equal to the ratio between the initial advancing velocity and the conveying velocity of the screw.

This application is a continuation of U.S. patent application Ser. No.12/993,021, filed Nov. 16, 2010, now U.S. Pat. No. 8,307,973 B2, issuedNov. 13, 2012, which is the National Stage Entry of PCT Application No.PCT/IB09/52000, filed May 14, 2009, the contents of each of which arehereby incorporated by reference herein.

FIELD OF THE INVENTION

The invention refers to techniques for the handling of article flows.

The invention was developed with particular attention to possibleemployment in the field of machines for the automatic treatment (forexample, for the packaging) of articles such as sanitary hygienicarticles (diapers, hygienic absorbent pads, etc.).

However, reference to this possible field of application should not beinterpreted as limiting of the scope of the invention.

DESCRIPTION OF THE RELATED ART

In the treatment of flows of advancing articles (for example, in thefield of machines for the production and packaging of hygienic-sanitaryarticles) the need often arises to selectively vary the separationdistance (or pitch) between subsequent articles in a flow and/or theneed to obtain an exiting flow constituted of groups of stackedarticles, starting from a flow of single entering articles.

The formation of such groups of stacked articles can be assigned todevices currently denominated “grouping devices”. An example of agrouping device is described in the document EP-A-O 943 562, assigned tothe present Applicant.

Such devices are often called on to operate on rather intense inputarticle flows (with intensities in the order of 1,000 articles/minute orhigher), and the number of articles comprised in each group identifiesthe functioning velocity of the grouping device. For example, a groupingdevice operating on an input flow of 1,000/minute and destined to formgroups of 10 articles each must be able to operate at a groupingvelocity equal to 100 groups/minute. In the language of the field, thesingle group is called a stack, and in the specific case considered thegrouping device is capable of 100 stacks/minute each stack composed of10 pieces. However, in a number of applications, the need arises to formgroups of articles containing a reduced number of articles, for example,two or three articles. Under such conditions, the nominal functioningvelocity imposed on the grouping device can become too high. Forexample, grouping devices with the highest performances currentlyavailable on the market provide performances of 100-200 stacks/minute.Equipment is also known that can produce 200 packages/minute: one suchequipment, combined with a 2000 piece/minute machine is thereforecapable of forming stacks of 10 pieces.

When the nominal functioning velocity imposed on the grouping devicebecomes too high and, in fact, is not attainable, one may be forced to:

-   -   reduce the intensity of the input flow, for example operating a        unit capable of producing 1,000 articles/minute at a reduced        velocity, in the order of 200-300 articles/minute; or    -   divide the input flow of articles into several sub flows (for        example, three-four sub flows, each with an intensity reduced to        one third or one quarter of the original flow) adapted to be        treated in an suitable way by as many grouping devices.

The first solution results in an obvious inefficiency from the point ofview of productivity, while the second solution translates into anotable burden in terms of complexity (and cost) of the machine; thisfactor is even more negative when the need to form groups with a reducednumber of articles is only temporary.

OBJECT AND SUMMARY OF THE INVENTION

In this general context, the need is felt for grouping devices availablecapable of forming groups of articles, such as sanitary articles (forexample, single use absorbent pad products) even containing a reducednumber of single articles (two or three) operating with cadencescompletely compatible with the elevated cadences (1,000/minute and more)found in treatment stations upstream.

According to the present invention, such object is achieved by means ofa device having the characteristics specifically recalled in the claimsthat follow. The invention also refers to a corresponding method.

The claims form an integral part of the technical disclosure providedherein relative to the invention.

In one embodiment, the invention is suitable for realizing a groupingdevice capable of operating, in a completely consistent and reliableway, at elevated functioning velocities that are completely compatiblewith the current functioning cadences of the production and workstations susceptible of being upstream.

In one embodiment, the device described herein is capable of simplyperforming the function of varying the separation step of the articlesin a flow, without providing any actually grouping of them.

BRIEF DESCRIPTION OF THE ANNEXED DRAWINGS

The invention will now be described, by way of non-limiting exampleonly, with reference to the annexed drawings, wherein:

FIG. 1 is a lateral elevation view of a device of the type describedherein,

FIG. 2 is a prospective view from above of the same device,

FIG. 3 is a schematic geometric representation useful to betterunderstand the functioning principle of the device described herein, and

FIG. 4 is a frontal elevation view approximately along the line IV-IV inFIG. 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the description that follows various specific details aimed at athorough understanding of the embodiments are illustrated. Theembodiments can be practiced without one or more of the specificdetails, or with other methods, components, materials, etc. In othercases, known structures, materials or operations are not shown ordescribed in detail to avoid obscuring the various aspects of theembodiments.

Reference throughout this description to “an embodiment” or “oneembodiment” indicates that a particular feature, structure orcharacteristic described relative to the embodiment is present in atleast one embodiment. Therefore, phrases like “in an embodiment” or “inone embodiment”, possibly present in various places in this descriptionare not necessarily referring to the same embodiment. Furthermore,particular features, structures or characteristics may be combined inany suitable way in one or more embodiments.

The headings used herein are for convenience only and thus do not definethe field of protection or the scope of the embodiments.

In FIG. 1 a device for the treatment of articles, such as, for examplehygienic sanitary articles A, is indicated in its entirety with 10. Inthe example illustrated herein, the articles in question indicated withA, are feminine hygienic absorbent pads of the three-fold type with eacharticle received inside a type of package currently denominated“flow-pack”. Naturally, the solution described herein is susceptible ofbeing applied to completely different articles, such as—for example—abi-folded baby diaper.

The device 10 illustrated herein comprises three conveyors indicatedwith 12, 14 and 16, respectively, destined to operate in a cascadedarrangement.

The conveyor 12 functions as the input conveyor of the device and isthus destined to receive a flow of advancing articles A (not necessarilyspaced from each other) and with a rather elevated cadence, for example,in the order of 1,000/minute. It will be assumed hereinafter that sucharticles advance with an input velocity indicated with v_(in).

According to a solution which is known by itself, the conveyor 12 iscomprised of a belt or chain structure, only the active branch of whichis shown in greater detail in the figures (in the exemplary embodimentit is the lower branch 120 with respect to an upper branch of the loopstructure, not expressly visible in the drawings) that has clipformations 122 at fixed distances essentially comprising spring clipsextending “backward” and overhanging in a cantilever fashion from theactive branch 120 of the belt with respect to the advancing direction ofthe conveyor 12, thus from right to left, with reference to the point ofobservation in FIGS. 1 and 2, that determine the separation step of thearticles A input to the device 10.

Therefore, each of the spring clip formations 122 forms a sort ofretaining pocket for a corresponding article A. The articles A areinserted into the formations 122 according to known criteria (whichtherefore do not require detailed illustration herein), under conditionssuch that, when slowed down with respect to the advancing velocityv_(in) imparted to them by the belt 120 of the conveyor 12, the articlesA tend to slide out from the formation 122 and to fall onto the conveyor16, representing the output conveyor of the device 10.

The conveyor 16 can be constituted by a motorised conveyor belt of whichin the figures only the upper transporting branch is visible.

The conveyor 14 operates in an intermediate position between the inputconveyor 12 and the output conveyor 16 with the possibility of realisingthe above-said slowing action on the articles A, sliding the articles Afrom the pockets of the conveyor 12 and causing them to fall onto theconveyor 16.

The description will specifically refer to the situation wherein thedevice 10 is used as a grouping device, that is, to generate an outputflow of groups of superimposed articles A, each group comprising, forexample, two superimposed articles, starting from a flow of articles Aarriving with a given advancing velocity (v_(in)). As will be betterseen hereinafter, the device 10 may be regulated so that the above-saidgroups of superimposed articles comprise three or more articles A.

The device 10 described herein is also suitable for being used to simplyvary the separation step of the articles A in passing from the conveyor12 to the conveyor 16, without providing the formation of groups ofsuperimposed article: from this point of view the formation of groups ofseveral articles stacked together can be seen as deriving from anextension of the action of varying the separation step betweensuccessive articles.

In the embodiment illustrated herein, the conveyor 14 is constituted bytwo rotating screw structures (cochleas) arranged symmetrically (moreprecisely mirror symmetry, also concerning the trend of thecorresponding helix/threads) with respect to the longitudinal advancingdirection of the articles A carried by the input conveyor 12 (on thisaspect, see the frontal view in FIG. 4).

The two screws 142 are generally mounted cantilever-like and protrudetowards the input extremity of the device 10 so that the articles Aarriving on the input conveyor 12 are inserted axially and advance inthe space comprised between the helices (or threads) of the two screws.

The screw conveyor 14 is thus adapted to receive a flow of arrivingarticles A longitudinally, that is, with the rotation axes of thehelices 142 (axes indicated with X₁₄₂) parallel to each other andparallel to the conveying direction of the articles A on the inputconveyor 12.

The pitch of the above-said helices is preferably selected so to be notless than the length of the articles A detected in the common advancingdirection on the input conveyor 12 and on the screw conveyor 14. In thisway, the articles A are able to advance for a certain segment inside theconveyor 14.

Those skilled in the art will appreciate also that such condition,although preferable, is not itself imperative for the purpose ofactuation of the functioning mechanism better described hereinafter.

The reference numeral 144 indicates a motorisation group capable ofrotating the two screws 142 in opposing directions, preserving themirroring condition of the angular positions instantaneously taken bythe portions of helix.

The rotational directions of the screws 142 are selected, to beconsistent with the winding or screwing directions of the correspondinghelices, so that the helices have an apparent winding movementconsistent with the advancing direction of the articles A (from right toleft, with reference to the observation point in FIGS. 1 and 2). In theembodiment described herein, it will be assumed that of the two screwsvisible in FIG. 2, the left one rotates clockwise and the right one,counter-clockwise. This said, the opposite choice is also possible.

FIG. 3 refers to some geometric parameters of a helix H considered as ageometric curve.

In particular, the represented helix H is a cylindrical helix with amain axis X_(H), radius R and pitch p.

Assuming to rotate such helix H around its axis X_(H) with an angularvelocity ω_(H) and assuming to indicate with g any one of the generatinglines of the ideal cylindrical surface on which the helix H lies, anypoint of the helix H will move along the generating g with a velocityv_(app) equal to ω_(H)×p.

This velocity v_(app) may be defined as the apparent axial screwingvelocity of the helix (and of the screw with corresponding geometry) oralso the conveying velocity of the screw.

The observer seeing the screw in question rotating around the axis X_(H)in fact has the impression of seeing it advancing axially with ascrewing velocity precisely equal to the above-said apparent screwingvelocity v_(app). At the same time, when the screw is used to conveymaterial (for example as the screw of an extruder) the velocity V_(app)in question is indeed the velocity with which the screw advances thematerial, conveying it in an axial direction with respect to the screwitself. The functioning of the device 10 described herein is in factlinked to the possibility of varying the rotational velocity of thescrews 142 around their corresponding axes X₁₄₂, by acting on themotorisation 144, so to precisely and selectively vary the velocityV_(app) with which the screws 142 themselves advance the articles A inarrival from conveyor 12.

In particular, assuming to adjust the rotational velocity of the screws142 so that the above-said conveying velocity v_(app) is equal to thevelocity v_(in) of the articles A in entrance, it is easy to understandthat under such conditions the articles A would advance along the screwswithout being subjected to modifications of their advancing velocity.

On the contrary, if the rotational velocity of the screws 142 isadjusted so that the above-said conveying velocity V_(app) is lower withrespect to the arrival velocity v_(in) of the articles A, the advancingmovement of the articles A will be correspondingly slowed down, when thearticles A advance axially between the two screws 142: this in factbecause the helices of the screws 142 extend radially so to interferewith the advancement of the articles A (see the representation in FIG.4). This slowing effect could be used, for example, to reduce theseparation space existing between articles A so to reduce suchseparation step in moving from the input conveyor 12 to the outputconveyor 16.

In the application illustrated herein, the above-said slowing effect isused to obtain groups of articles A in exit on the conveyor 16.

In particular, if the rotational velocity of the screws 142 is regulatedso that the conveying velocity v_(app) is equal to half the entrancevelocity v_(in), once having arrived in the space comprised between thescrews 142, the articles A advance at a velocity equal to half that oftheir previous velocity; therefore, in a given time, when conveyed bythe screws 142 they travel a distance equal to half of what they wouldhave travelled when transported by the input conveyor 12.

Due to the effect of such slowing, the articles A “slide out” of thepockets formed by the grasping formations 122 so that they fall onto theconveyor 16 below, which is also made to advance with a velocity equalto v_(app), thus equal to half of the input velocity v_(in).

The effect obtained by slowing to the velocity v_(app) equal tov_(in)/2, by the “sliding out” from the formations 122 of the conveyor12 and by falling onto the conveyor 16 (keeping, however, the advancingvelocity equal to v_(app)) is in fact the formation of groups of twoarticles A superimposed on the conveyor 16 advancing at the velocityv_(app).

The above-said mechanism may be extended to the formation of groupscomprising any number n of stacked articles A by reducing the angularvelocity of the screws 142 so that the above said conveying velocityv_(app) (that is, the velocity with which the threads or helices of thescrews 142 oppose the advancing of the articles A, slowing them) isequal to a sub multiple 1/n of the velocity v_(in) (that is, applyingthe formula v_(in)/v_(app)−n)

In this way, once they are received between the screws 142, the articlesA, in fact, advance at a velocity that is equal to 1/n^(th) of theentrance velocity v_(in). For a given time, the articles A advancingbetween the screws 142 travel a distance equal to 1/n^(th) the distancethat they were travelling in the same unit of time, when moved by theconveyor 12.

As in the case of the formation of groups of two stacked articles A, theslowing action does not translate into a disordered overlaying of thearticles A one against the other: as soon as it slides out of thecorresponding formation 122, each article A falls on the conveyor 16 andcan receive onto itself the article A that slides out immediately afterfrom the formations 122 of the conveyor 12.

Those of skill in the art will appreciate that, in practice, the choiceof the number n is conditioned only by maintaining the coherence of thestacks of superimposed articles A. On the other hand, the solutiondescribed herein was developed with particular attention to its possibleemployment for the realisation of groups of stacked article comprising areduced number of articles (a few units, at most).

It will also be appreciated that the device 10 described herein operatesaccording to an “online” functioning criteria, with a plurality ofconveyors operating in a cascaded arrangement. This allows the device 10to function with very elevated functional cadences, totally compatiblewith flows of entering articles A in the order of 1,000 articles/minuteand higher.

While the present description refers to the employment of the screws 142as a means of slowing the advancing movement of the articles A, the samemechanism allows—always playing on the rotational velocity of the screws142, and therefore on the variation of the conveying velocity v_(app) ofthe articles A by the screws 142—to determine an acceleration of themovement of the articles A so to produce an increase in the separatingstep between the articles themselves.

Furthermore, the embodiment illustrated herein refers to screws 142having a constant pitch p. However, the solution described herein issuitable for being actuated with a non-constant pitch, for example, witha pitch that decreases starting from the entrance extremities towardsthe exit extremities of the screws (going from right to left, withreference to the observation point in FIG. 1 or 2). In otherembodiments, instead, the pitch of the screws 142 can increase startingfrom the entrance extremity towards the exit extremity of the device 10itself. In addition, while the solution described herein envisions theemployment of continuous helix screws 142, the solution described hereinis also suitable for being realised taking recourse to screws withhelices that are constituted by distinct segments. Finally, even if thesolution described herein envisions the employment of two screws 142arranged side-by-side the basic mechanism of the solution describedherein can also be actuated using only one screw.

Consequently, without prejudice to the underlying principle of theinvention, the details of realisation and the embodiments may varywidely with respect to what has been described and illustrated herein,without departing from the scope of the invention as defined by theannexed claims.

What is claimed is:
 1. A device for generating, from a flow of incomingarticles with a given advancing velocity (v_(in)), an output flow ofsaid articles comprising: an input conveyor; a screw conveyor configuredto receive longitudinally said flow of incoming articles from said inputconveyor, said screw conveyor including at least one screw having ahelix configured to interact with said advancing articles to control theconveying of said articles by said at least one screw, a rotationalvelocity (ω) of said at least one screw being selectively adjustable tovary a conveying velocity (v_(app)) of said articles by said at leastone screw with respect to said given advancing velocity (v_(in)); and anoutput conveyor configured to receive from said screw conveyor saidoutput flow of said articles, wherein said input conveyor has a loopstructure and is provided with retaining formations configured toreceive said incoming articles, said retaining formations extending fromsaid loop structure, and wherein said at least one screw is adapted tointeract with the articles conveyed by said input conveyor causing saidarticles to slide out of said retaining formations.
 2. The deviceaccording to claim 1, wherein said at least one screw has a constantpitch.
 3. The device according to claim 1, wherein said at least onescrew has a pitch not less than a length of said articles in anadvancing direction of said flow of incoming articles.
 4. The deviceaccording to claim 1, wherein said screw conveyor includes at least onepair of said rotating screw configured to be rotatable in conditions ofmirror symmetry with each other.
 5. The device according to claim 4,wherein said screw conveyor is configured to convey said incomingarticles in interposed positions between said at least two one pair ofsaid rotating screws.
 6. The device according to claim 1, wherein saidoutput conveyor is movable with a velocity equal to said conveyingvelocity (v_(app)) of said articles by said at least one screw.
 7. Thedevice according to claim 1, wherein said retaining formations open in adirection opposite to an advancing direction of said articles on saidinput conveyor.
 8. The device according to claim 1, wherein said outputconveyor is located at a lower level than said screw conveyor such thatsaid output conveyor is configured to receive said articles dropped fromsaid screw conveyor in said output flow of said articles.
 9. A devicefor generating, from a flow of incoming articles with a given advancingvelocity (v_(in)), an output flow of said articles comprising: an inputconveyor; a screw conveyor configured to receive longitudinally saidflow of incoming articles from said input conveyor, said screw conveyorincluding at least one screw having a helix configured to interact withsaid advancing articles to control the conveying of said articles bysaid at least one screw, a rotational velocity (ω) of said at least onescrew being selectively adjustable to vary a conveying velocity(v_(app)) of said articles by said at least one screw with respect tosaid given advancing velocity (v_(in)); and an output conveyorconfigured to receive from said screw conveyor said output flow of saidarticles, wherein said input conveyor is provided with retainingformations configured to receive said incoming articles, wherein saidretaining formations open in a direction opposite to an advancingdirection of said articles on said input conveyor and wherein said atleast one screw is adapted to interact with the articles conveyed bysaid input conveyor causing said articles to slide out of said retainingformations.
 10. The device according to claim 9, wherein said at leastone screw has a constant pitch.
 11. The device according to claim 9,wherein said at least one screw has a pitch not less than a length ofsaid articles in an advancing direction of said flow of incomingarticles.
 12. The device according to claim 9, wherein said screwconveyor includes at least one pair of said rotating screw configured tobe rotatable in conditions of mirror symmetry with each other.
 13. Thedevice according to claim 12, wherein said screw conveyor is configuredto convey said incoming articles in interposed positions between said atleast one pair of said rotating screws.
 14. The device according toclaim 9, wherein said output conveyor is movable with a velocity equalto said conveying velocity (v_(app)) of said articles by said at leastone screw.
 15. The device according to claim 9, wherein said inputconveyor has a loop structure with said retaining formations extendingfrom said loop structure.
 16. The device according to claim 9, whereinsaid output conveyor is located at a lower level than said screwconveyor such that said output conveyor is configured to receive saidarticles dropped from said screw conveyor in said output flow of saidarticles.
 17. A device for generating, from a flow of incoming articleswith a given advancing velocity (v_(in)), an output flow of saidarticles comprising: an input conveyor, wherein said input conveyor isprovided with retaining formations configured to receive said incomingarticles and wherein said input conveyor has a loop structure with saidretaining formations extending from said loop structure; a screwconveyor configured to receive longitudinally said flow of incomingarticles from said input conveyor, said screw conveyor including atleast one screw having a helix configured to interact with saidadvancing articles to control the conveying of said articles by said atleast one screw, wherein said at least one screw is adapted to interactwith the articles conveyed by said input conveyor causing said articlesto slide out of said retaining formations, a rotational velocity (ω) ofsaid at least one screw being selectively adjustable to vary a conveyingvelocity (v_(app)) of said articles by said at least one screw withrespect to said given advancing velocity (v_(in)), and wherein saidscrew conveyor includes at least one pair of said rotating screwconfigured to be rotatable in conditions of mirror symmetry with eachother; and an output conveyor configured to receive from said screwconveyor said output flow of said articles.
 18. The device according toclaim 17, wherein said at least one screw has a constant pitch.
 19. Thedevice according to claim 17, wherein said at least one screw has apitch not less than a length of said articles in an advancing directionof said flow of incoming articles.
 20. The device according to claim 17,wherein said screw conveyor is configured to convey said incomingarticles in interposed positions between said at least one pair of saidrotating screw.
 21. The device according to claim 17, wherein saidoutput conveyor is movable with a velocity equal to said conveyingvelocity (v_(app)) of said articles by said at least one screw.
 22. Thedevice according to claim 17, wherein said retaining formations open ina direction opposite to an advancing direction of said articles on saidinput conveyor.
 23. The device according to claim 17, wherein saidoutput conveyor is located at a lower level than said screw conveyorsuch that said output conveyor is configured to receive said articlesdropped from said screw conveyor in said output flow of said articles.